Electrostatically charged tobacco smoke filter



Aug. 26, 1969 J. H. TROLL. ET AL 3,

ELECTROSTATICALLY CHARGED TOBACCO SMOKE FILTER Filed April 27, 1967 2202224 H66 H660 80 H68 Attorneys By Dow's,Hox/isg'Fa/fhfullaHapgooo' Y United States Patent U.S. Cl. 131-262 3 Claims ABSTRACT OF THE DISCLOSURE A tobacco smoke filtering means having passageways through which the smoke passes, the passageways being defined by dielectric material permanently electrostatically changed to provide a negative and a positive charge in series alignment.

INTRODUCTION This is a continuation-in-part of copending patent application Ser. No. 372,182 filed June 3, 1964, entitled Tobacco Smoke Filter, and now abandoned.

This invention relates to a product and method for the removal of harmful portions of tobacco smoke. More particularly, it relates to a filter and method for removing from tobacco smoke positively charged particles, negatively charged particles and electrostatically neutral particles by electrostatic attraction onto the surface of a polarized dielectric material.

Recent scientific evidence has established the presence of electrostatically charged and uncharged particles and radio-active elements, in particular Polonium 210, in cigarette smoke which enter the smokers bronchial airways and produce various harmful elfects amongst which are carcinogenic eifects and a causal relationship or, at least, an association with bronchitis, emphysema, cardiovascular and other diseases. One of the principal factors involved which can be considered a cause of these detrimental effects is the inhibition of the cilial activity through which particles are removed from the bronchial air waves. Such inhibition apparently enables environmental carcinogens to reach the epithelial cells. It has been shown that positive ions are a cilial depressant and such ions may be derived from alpha particle reduction of Polonium 210. Furthermore, radio-active Polonium 210 is negatively charged, thus explaining the presence of at least one type of harmful electrostatically negative particle. The radiation dose absorbed by smokers is substantial and, furthermore, the synergistic action of ionizing radiation with the other chemical agents present in tobacco smoke may have a significantly detrimental effect. In addition to these electrostatically charged particles, there also are present in tobacco smoke a large number of neutral colloidal particles whose physical presence in the bronchial airways may be harmful. Some arise, for instance, from negatively charged Polonium 210 combined with positively charged ions. The Polonium particles continue as radio-active colloidal particles which should be filtered out of the smoke.

BACKGROUND Previous filters relied upon mechanical traps which, no matter how efiicient, do not remove the harmful ingredients of the gaseous phase of the smoke. Electrostatic filters have been developed for removing particles of a single electrostatic charge only. Many of these filters require an external electric power source. This invention provides a filter that specifically removes particles which are positively charged, negatively charged and neutral from the mainstream of the smoke before they make contact with any portion of the smokers anatomy without requiring any external source of electric power and without altering materially the physical shape of, or established manufacturing procedures for, tobacco or tobacco articles such as cigarettes. The removal is performed by causing the tobacco smoke to flow adjacent to filter elements which have dual electrostatic charges; i.e., positive and negative, in series alignment with the smoke flow path.

Accordingly, it is one object of this invention to provide an improved tobacco smoke filter and method for removing positively charged, negatively charged and neutral particles from tobacco smoke.

It is another object of this invention to provide such a filter which is exceptionally efficient, inexpensive to produce and utilize, and which can be readily adapted for use with any type of smoking article.

BRIEF DESCRIPTION Certain materials are particularly suitable for use as a tobacco smoke filter since they are capable of being electrostatically charged and holding their charge for long periods of time, for example two years and more. Such materials, which are considered to be permanently charged, are dielectrics and are referred to herein as electret material and the material when changed is called an electret. Electrets may be introduced directly into the tobacco of the smoking article or may be incorporated into a separate unit through which the tobacco smoke flows prior to entry into the smokers bronchial airways. It is importantthat such filters include electrets having both positive and negative charges and that the electrets 'be arranged such that the tobacco smoke, in passing through the smoking article, contacts electrets of both polarities. The positively charged electrets attract the negatively charged particles, the negatively charged electrets attract the positively charged particles and the neutral particles, upon being exposed to electrets of one polarity, will become charged with that polarity and be attracted to the subsequently encountered electrets of the opposite polarity.

This invention, in one form, comprises a cigarette filter intended to be placed on the month end of a body of cigarette tobacco. The filter is formed of a plurality of cylindrical passageways, formed in electret material, through which the tobacco smoke passes. Each passageway is charged positively for a portion of its length and negatively for a portion of its length.

Another form of this invention is to intermix electrets having positive and negative charges with the tobacco throughout the tobacco body. A large number of such electrets randomly scattered throughout the tobacco provides the series alternation of differently charged electrets to adequately filter the tobacco smoke.

DRAWING These and other forms embodying this invention are illustrated in the following drawing in which:

FIGURE 1 is a quarter sectional view of a cigarette having a filter formed in accordance with a first embodiment of this invention.

FIGURE 2 is an end view of the filter of FIGURE 1.

FIGURE 3 is an exploded view of a mold apparatus for producing the filter of FIGURE 1.

FIGURE 4 is a sectional view of a cigarette having a filter formed in accordance with a modification of the first embodiment of FIGURE 1.

FIGURE 5 is an end view of the filter of FIGURE 4.

FIGURE 6 is a sectional view of a filter formed in accordance with a second embodiment of this invention.

FIGURE 61: is a magnified view of a portion of the filter of FIGURE 6.

FIGURE 7 is a schematic illustration of a method of forming spherical electrets employed in the filter of FIG- URE 6.

FIGURE 8 is a partially cut away view of a cigarette formed in accordance with a third embodiment of this invention.

First embodiment (FIGURES 1 and 2) Referring now to the drawing and, more particularly to FIGURES l and 2, there is illustrated a conventional cigarette 10 having on the end 12 thereof a filter 14 formed in accordance with a first embodiment of this invention. The filter 14 is formed from an electret material 16 in cylindrical form and having a plurality of tunnels or tobacco smoke passageways 18 extending longitudinally therethrough. The filter 14 is divided longitudinally into a plurality of zones, four being illustrated at 20, 22, 24, 26. The tunnel walls are provided with an electrostatic charge and the zones are arranged such that adjacent zones have opposite polarities. For example, in FIGURE 1 the tunnels of the first zone 20 have a positive charge, the tunnels of the second zone 22 have a negative charge, the tunnels of the third zone 24 have a positive charge, and the tunnels of the fourth zone 26 have a negative charge. While four zones are illustrated only two are necessary to provide efficient filtering. In this manner, smoke from the tobacco portion of the cigarette 10 enters the tunnels 18 and is exposed to both a positive and negative charge before entering the smokers bronchial airways.

Although not illustrated, it may be desirable to provide an electrically non-conductive, non-toxic material between adjacent zones as this will prolong the maintenance of the electrostatic charge on the tunnels 18.

FIGURE 3 illustrates one way of making the electrostatic filter 14. A cylindrical mold 28 open at both ends is formed of a non-conductive material such as lava or other alumina ceramics. The inner surface of the mold is lined with an electrically conductive material such as copper, the lining 29 having an inside diameter approximately equal to the outside diameter of a cigarette. Within the mold 28 a plurality of conductive wires or rods 30 are longitudinally suspended by electrically non-conductive support discs 32, 34. The discs can also serve as end walls for the mold 28. In order to facilitate removal of the solidified filter from the mold, it is necessary to coat the inner surface of the liner 29 and the outer surface of the rods 30 with a suitable mold lubricant such as polytetrafluoroethylene. The rods are electrically connected to one of the poles of a DC current source 35, for example the positive pole, while the mold liner 29 is electrically connected to the other pole of the DC current source 35.

Electrostat material in molten form is then poured into the mold 28 and a high voltage, on the order of 10 kv./cm., is impressed across the rods 30 and liner 29. Some materials which can be polarized and considered electret material are glass, organic resins such as polyethylene, terephthalate, carnauba wax, beeswax, polar hydrocarbons, esters, alcohols and asphalt. It has been found that glass is especially suitable for use as a filter and that in order to provide the glass with a permanent electrostatic charge it is only necessary that the glass be exposed to a strong D.C. field, while in the molten state and be allowed to solidify while still being exposed to the D0. field. When the molten glass is exposed to such a field, a charge on the order of 30 e.s.u./cm. will be produced.

It is understood that while a batch method for producing the filter has just been described, the method is suitable for adaptation of a continuous processing by conventional extrusion molding procedures.

4 Modification of first embodiment (FIGURES 4 and 5) An alternative form of the above described first embodiment is illustrated in FIGURES 4 and 5 wherein a filter 36 is provided with a plurality of tunnels 38 having different electrostatic charges within each longitudinal zone. Two zones 40, 42 are illustrated, although more may be employed. The tunnel pattern within the first zone 40 comprises three concentric circular rows of tunnels 38, the outermost and innermost rows 44, 46 respectively be ing of one polarity (positive) while the intermediate row 48 is of the opposite polarity (negative). While only three concentric rows are shown, in practice a substantially larger number of rows are used with adjacent rows having opposite polarities. The tunnel pattern within the second zone 42 is identical to the first zone except that the polarities of the rows are reversed, i.e. the outermost and innermost rows 50, 52, respectively, are negatively charged while the intermediate row 54 is positively charged.

Each zone of the filter 36 may be produced by substantially the same method as described above with respect to the production of filter 14 except that there is no need for the molds conductive liner 29. In order to make the filter 36 the adjacent rows of conductive rods 30 are electrically connected to opposite sides of the DC. current source. The dielectric electret material acts as a capacitor and the surface of the tunnel immediately surrounding each rod is given a charge of the same polarity as the rod which it surrounds. To form an adjacent zone it is merely necessary to reverse the polarities on the rods thereby producing a filter zone having the same pattern but reversed electrostatic charges in the tunnels. As mentioned earlier this can be performed as a batch process or a continuous extrusion process.

A pressure differential across the filter, such as is caused by inhalation by the smoker, causes the tobacco smoke to pass longitudinally through the tunnels and, before entering the smokers bronchial airways, the smoke will pass through at least two zones of opposite polarity. When the smoke is in the first zone the particles having a polarity opposite to that of the tunnel in which the smoke is in are attracted to the surface of the tunnel and are removed from the mainstream. The electrostatically neutral particles will become charged with the charge of the tunnel to which they are first exposed. As the smoke progresses through the filter it is then exposed to the second zone wherein the tunnel has a polarity opposite to that which it had in the first zone. In the second zone those particles not removed from the first zone are removed because the particles remaining are those which had a charge, either initially or induced by the first zone, of the same polarity as the first zone tunnel. When the particles enter the second zone, their polarity will be opposite to that of the second zone tunnel and, accordingly, they will be attracted to the tunnel surface and removed from flow stream.

While two tunnel patterns were described above in connection with FIGURES 1, 2 and 4, 5, it is clear that many other tunnel patterns can be employed. Furthermore, while individual, cylindrically shaped tunnels are described it is clear other shapes which can be molded may be utilized. The critical feature is that the smoke which enters the tunnels is exposed to a positively charged zone and a negatively charged zone before the smoke exits from the filter.

Second embodiment (FIGURE 6) A second embodiment of this invention, illustrated in FIGURE 6, comprises a filter 60 adapted to be attached to the mouth end of the cigarette (not shown). The filter is formed of a mass of spherical electrets 62 packed under force into a cylindrical container 64 formed of plastic or stiffened paper. The spherical electrets 62, which preferably are of glass or a polyester resin, are formed as illustrated in FIGURE 7. Electret material 66 in a molten state is contained under pressure within a hopper 68 and spherical droplets 70 of the molten electret material are ejected from the exit nozzle 72. The droplets pass between electrically charged plates 74, 76 having opposite polarities with suflicient velocity so that the moment inertia of the droplets is larger than the electrostatic moments impressed upon the solidifying droplets. The resultant electrets 62 of spherical shape are hemispherically charged or, in other words, the hemisphere adjacent to the positive plate 74 will be charged positively while the hemisphere adjacent to the negatively charged plate 76 will be charged negatively. FIGURE 6a illustrates a magnified portion of FIGURE 6 to illustrate the hemispherical charges and a probable electret alignment.

Spherical shapes are preferred over other rounded forms in order to assure minimal contact between the adjacent electrets resulting in multiple heavily charged passageways 78 of sufilcient cross-sectional area to permit a proper toacco smoke flow stream. Furthermore, reduction of the contact area between adjacent electrets assures maintenance of the charges on the electrets for a sufiiciently long period, considering their intended use. It will be observed that the hemispherical charges on the electrets assures that the tobacco smoke will be in contact with or immediately adjacent to surfaces of both positive and negative charges during its passage through the filter.

Third embodiment (FIGURE 8) A third embodiment of this invention, illustrated in FIGURE 8, comprises the use of electrets 80 having a particle size smaller than the width of tobacco shreds employed in the finished tobacco product, such as a cigarette 82. In order to prevent the eletcrets 80 from being inhaled in the event that no other filtering medium is employed, the electret particle size is substantially larger than the average diameter of the smoke passageways between tobacco shreds or between tobacco and paper wrapper. It has been found that the electrets should be larger than about .005 inch. If a mechanical filter tip of the conventional type is employed, the electrets may be smaller since they will be prevented from entering the smokers bronchial airways by the mechanical filter.

The electrets, preferably of glass or other electret material having a melting point above the temperature to which it will be exposed, are activated by allowing them to pas sfrom a molten to a solid state in the presence of a strong D.C. electric field as described above. The proper size may be obtained by dividing the electrets into particles of the desired size by any conventional means such as ejecting the molten material through fine spray nozzles, screens, or by subjecting the solidified electrets to any conventional comminuting means. The electrets are then sprayed upon or mixed with the tobacco leaves or shreds, adhering to them by electrostatic attraction. Alternatively, they may be mixed and dispersed in an electrostatically neutral, non-conductive, non-toxic and non-volatile adhesive and sprayed on the tobacco leaves or shreds. During smoking, the permanently charged electrets 80 attract the positively charged portions of the tobacco smoke to their negatively charged portion of the surface and the negatively charged portions of the tobacco smoke to their positively charged portions of their surface thus effectively filtering the tobacco smoke.

FIGURE 8 illustrates that random dispersement of the electrets throughout the length of the cigarette assures that the tobacco smoke will flow adjacent to both positively charged and negatively charged surfaces throughout its flow stream.

While the above description has been directed primarily to cigarette filters, it is clear that the principles of this invention are equally applicable to filters for other smoking articles, such as cigars and pipes. Furthermore, when used they can be filters permanently mounted on cigarettes or cigars or as disposable inserts for reusable, separate filters which are adapted to receive the smoking article.

As will be apparent to those skilled in the art, various other modifications can be carried out from the above disclosure without departing from the spirit and scope of the invention.

What is claimed as new is:

1. An improved tobacco smoke filter, adapted to be used with a tobacco article, comprising a body of electret material having a plurality of tunnels therethrough, said material surrounding a first portion of each of said tunnels being negatively charged and said material surrounding a second portion of each of said tunnels being positively charged, said tunnel portions being in series flow relationship with each other, whereby smoke from said article flows through said tunnels, thereby being exposed to said negatively and positively charged portions.

2. A filter as defined in claim 1 wherein said body of electret material includes at least two longitudinally adjacent zones, all of the tunnel portions in one of said zones being negatively charged and all of the tunnel portions in an adjacent zone being positively charged, the tunnel portions of said zones being aligned in series flow relationship.

3. A filter as defined in claim 1 wherein said body of electret material includes at least two longitudinally adjacent zones, some of the tunnel portions in each of said zones being negatively charged and the remaining of the tunnel portions in each of said zones being positively charged, the tunnels portions of the adjacent zones being aligned so that oppositely charged tunnel portions in the respective adjacent zones will be aligned in series flow relationship.

References Cited UNITED STATES PATENTS 2,740,184 4/ 1956 Thomas 2878 2,990,912 7/1961 Cole 55130 3,079,930 3/1963 Cobb et a1. 131267 3,087,500 4/1963 Jacobson 13110 3,240,212 3 1966 Royster 131-9 FOREIGN PATENTS 433,048 8/1935 Great Britain.

MELVIN D. REIN, Primary Examiner D. J. DONOHUE, Assistant Examiner US. Cl. X.R. 131-105, 10.7, 17 

